Multirange tuner for ultra high frequency transmitters



March 23, 1948. J. M. DODDS ET AL MULTIRANGE TUNER FOR ULTRA HIGHFREQUENCY TRANSMITTERS Filed Dec. 29, 1943 0 JIVUQ/MOW vawlim WWW John MDpflds, JoiznM Lyd low,

29 1 v 30 33%! 5'3 30 K5 Fig-z lv CD3 Patented Mar. 23, 1948 QFFICEMULTIRANGE TUNER FOR ULTRA HIGH FREQUENCY TRANSMITTERS John MathiesonDodds, Timperley, and John Heywood Ludlow, Bowdon, England ApplicationDecember 29, 1943, Serial No. 516,104 In Great Britain May 13, 1938 13Claims. 1

This invention relates to radio transmitters of the kind in whichprovision is made for changing expeditiously the wavelength oftransmission by the substitution of different tuning inductances the onefor another. Such arrangements are mostly employed in transmittersoperating on relatively short wavelengths such as in the range of from13 to 70 metres which is used for beam working wherein owing to changesin conditions of propagation an alteration of wavelength is usually tobe effected frequently in order to ensure reasonable continuity ofservice.

In general, the wave changing arrangements comprise a number ofinductances or tuned cincuts mounted upon a rotating structure orturntable each inductance being provided with switch 1 contacts so thatany one of the inductances or tuned circuits can be connected to theassociated power valve or valves. Such arrangement permits the change tobe made in a relatively short time. Since on beam stations a separateaerial array is used for each wavelength, a selector switch has also tobe operated to connect the appropriate feeder lines to the transmitter.In the use of such a rapid wave changing arrangement, having rotated theturntable to substitute one inductance or tuned circuit for another, theoperator then sets the various variable tuning condensers topredetermined positions or values and causes the power to be applied, afinal adjustment of the tuning condensers being usually necessary.

In our application Ser. No. 516,103 for Radio transmitters, filedDecember 29, 1943, wave changing arrangements are described involvingswitch arms for selectively connecting a plurality of fixed inductancesto terminals of push-pull valves. It will be appreciated that in spiteof the dimensioning and arrangement set forth in that application, owingto the finite inductance of the switch arms and the displacement of theinductance coils laterally from the valves, the minimum possiblewavelength at which the valves can efiiciently operate is not achieved.The present invention is based on the consideration that when it isdesired to resonate the valves to the minimum wavelength which can beachieved without recourse to series condensers, a satisfactoryperformance can be obtained when the inductance comprises a shortstraight wide bar connected directly between the electrode terminals andelectrically weld joined to the latter. The inductance loop thencomprises the bar and the electrode terminals of the two valves, theelectrodes themselves and the supports of the electrodes. Such loop cansatisfactorily be used for feeding in or feeding out high frequencyenergy by magnetic or other coupling means.

Regarding the mention in the preceding paragraph of the use of a seriescondenser, in many circuits when high power is handled at relativelyhigh voltages, the series condenser if used effectively must have thesame order of capacity as that between the valve electrodes. It will beappreciated therefore that the use of such a series condenser becomesdifficult, owing to the high voltage developed across it, particularlyin an anode circuit. If the condenser is of the air dielectric type itis inherently of large size in order to withstand the voltage and thisfact, coupled with its high inherent inductance, is considered tooutweigh the advantage otherwise derived from the use of such condenser.On the other hand other types of condenser than air dielectriccondensers are generally found to be unsatisfactory on the very shortwavelengths in question.

The object of the present invention is a rapid wave changing arrangementwhich permits the minimum possible wavelength to be achieved. Ashereinbefore indicated the free radial length of the switch blades setforth in said application Serial No. 516,103 cannot be made less thanthe clearance required between the pairs of contacts or jaws to whichthe respective inductances are attached and between such adjacent partsas are alive when the switch is in another position to that which itoccupies when in position to connect the selected inductance to theelectrodes.

The present invention provides an arrangement by which the presence ofthe switch does not substantially affect the minimum wavelength to whichthe valves can be resonated, at least in one position of the switch.

According to the present invention the improved inductance wave changingarrangements comprise the electrode terminal member of a valve whichterminal member has a switch contact face, an inductance terminal memberhaving a contact face preferably parallel with the face of the electrodeterminal member and spaced apart only a sufficient distance safely towithstand the working voltage stresses between said faces, and a movablecontact blade or bridge having two opposite contact faces adapted toengage between the aforesaid two contact faces. The fixed terminalmember of the inductance has or is adapted to have secured to it aninductance which for the minimum possible wavelength is a straight widebar, that is to say wide in the direction par- 7 ther t ml arla;ic-andecir se h l d rr allel with the axis of the inductance loop formedthereby. The electrode terminal member may have a plurality of contactfaces or alternatively it may have an extended contact face. Adjacentsaid other contact face or another part of the extended contact face maybe arranged a further fixed induetances terminal member, so that bymoving said bridge frolnione position-to another or employingtwdalternatively operable bridges, the value of the inductance may bevaried, the secnd or the further inductances having for instance asemicircular loop, a complete turn. or

more than one complete turn. Preferably the arrangement set forth isduplicated,.that isto say there is a bridge or blade member on ie ach side o f the inductance, the arrangement being symmetrical with respectto the i-nductange extended V tances .of -.-difierent,yalue in. thearrangement abov set; forth. one; or .more..of ,.the= inductances maybevariable-andcomprise a pair 'of parallel bars withtwhich the bridge orblade members are adapted. to make contact ashereinbefore.

verse inductance bar. .or

t tedw i e a bridge :is: slidably. arran ed-between said parallel bars.so that the inductancevalue can: be changed as desiredf' .l v

I-he-.;inventron.above.set forthmay be combined with; the inventionforming the subject of the above mentionedapplication Serial No. 516,103filed of even dateherewithby :using the aforesaid bridges or arms inconjunction with theswitch jaws or the equivalent to which apluralityoffixed inductancf'es; "are.-attached '.'in the, manner .describedin:that.lapplication,the arrangement being such that the straightinductance bar-,(or

adjustablebridge) can b.e1-used when desired for V operation o n thewavelength. [The blade maybe wide in the axial direction throughout itslength although its-width l is-actually. only required: e cb a h -t e' fq it t e clearances as hereinb ore mentiqnecl in the minimum ave c itine 7. 1-131. 7

eefi ren i eie r. cgm ris ei Q W E bsidiary f eature When-{applied morepar- 1 tweenth ane iem nel a high power va nd terminal ohthe otherelectrodes is that the anode terminal'usually hasconsiderably greater.axial length, at least irr-thecase of fluid cooled yalves-ofthe-metalenvelopetype; It will thus-be tappreciatedithatrastraight bar type ofinductance maybe connected directly between the anodes ;of a pair-oivalves at any level within th engths of ,the anodes w'I-fhe positionloffthe bar-forminimumwavelength would beat .the end of the anodes nearestto the terminalsoi the electrodes'with whichthe anodes are beingresonated. A particular advantage in this connection arises from thefact that; the'lengtlreif thess witch bar or bladeis of the same gorderas that or the axial. length ofthe anode. Therefore according to thisfeature of the invention the hinge of the bridge or bladermay'fbearrangedat thatilen'd of the. we. recesses-9c ages-recener Thevalves are preferably minimum wavelength as just above mentioned. Thusthe switch blade may in one position be closed along the length of theanode so that in this position it makes contact with a contact race 5 ofthe anode in a position remote from the hinge, Y

whilst simultaneously in this position making contactiwitlrvarrinductance terminal, to which may be -con'nected the straight bar, otherpositions of the blade other inductances may be connected to theelectrodes. To enable the invention to be clearly under- :stoodcertain;considerations leading thereto and certain arrangements thereof by wayof example will now be described With reference to the ac-,companying-drawings in which:

Figure l is a simplified diagram illustrating the fundamentakprincipleof the present invention. Figure 2 isa similar diagram showing oneembodiment of the present invention.

Figures 3 and 4 are front and 'side elevations of. aimore. practicalform, of. the invention, and j, Figure 5,,fis ,a plan yiew, ,of a"modification Qof the V Eiguresfi and 7. areanelevationjand. planr'epectiye bf. a1further-modificat o f t e nvention;

Refin .rst top f g. 1 .o ,.t e a' zq0mpah n drawings it is to be assumedthat, as. hereinbeforeset forth two, similar valves injiaccordanceWithJBritish Letters Patent Nm 41. .4753 arelope erated.inpush,-pull andthe .anode circuit is res,- o'nated to the ,eflfictively earthedscreening grids. Fiesland 2.. which. urely i g amma ic and 1O Z --W .jii i$. det ls a em t. ro e;c ea the basic. ir nit 'ny tcdm a c rdanca-wih. hein resent nve, 1011- .11 9 synol r present the amdes an th s r wingridsof a pair of. valves operated inpush-pull. ach a odeisslm orted nanxi n u atin qnv qp 'p .3 nd th te m nal 4 of ea h ,SPIQQQ; inggrid'.is led outannularly and. istefiectively onne te o. a .asthe high e ncqurreets a a on rne eart1. .l .a .reprc en ed'ai E h an a ecess t a cqnsdcrable externallength, it being assumed that theane dei ygt k pplai ans itu e a pore 1iJQ9 l F fi e-' v. inductance mophus formed will-Warywith-the pos iiwi the s ams-J al n ma et- The nearer 'is"th" ap-'nam'ely*=as india d a't 1, tofihe screenf g--gri d terminalfig'thesmaller Y R ferring. 159% 9 37 .t el .t e.. eenunvens n. the avesm y; bqau ed. .i'o llaia'atili W et ime r g se s: a

' cncisg h a delis ol taqtff D 1 d etaifi if spi er-wai contact. faces:t2 and the gapbetween each face l and IE2 is made a minimum butv alwayssuflicient to withstand: the'working voltage stresses between saidfaces. The gap t3 between said faces is adapted; to. have inserted in ita movable contact bridge which is not shown in Fig. 2. When said bridgeis thusv in position the valves will clearly operate. at the. minimumpossible wavelength. When said contact bridge is removed the inductance.H is no longer in circuit and. the anodes can be connected to anotherinductance. and; to this end the movable bridge may be; in the form of apivoted or otherwise movable switch arm.

In aparticular arrangement illustrated by Figs. 3 and 4 each anode Ioritsv preferably integral terminal has: pivoted to it at I4 the movableblade or bridge l5; the. pivot M being at that end of the anode which isremote from the: screening grid terminal (not. shown in Figs. 3 and 4).Thus when the pivoted switch contact blades or bridges [5 are in thepositions shown in Figs. 3 and 4 the inductance strap or bar H isconnected directly between the lower ends of the anodes. The member H ispreferably wide in the direction which is parallel, with the axis of theinductance loop of which said member H forms a part.

By simultaneously swinging. the. two movable bridge members. away fromtheir illustrated positions said movable :bridge members may be causedto engage any one of the pairs of jaw or other contacts l6, I? and I3(Fig. 4) which are mounted on pillars or on a panel 59 and are connectedrespectively to inductance coils 28, 2! and 22. The member is shown in.dotted lines at l5a as connecting the inductance coil 2! through theinductance terminal contacts H to the anodesof the two valves.

At the lower part of Fig. 4 is shown a corresponding wave changingarrangement for the grid circuit, the member [5 in this case beingpivoted to the grid terminal 23. For the minimum wavelength the member15 engages jaws 24' which are connected to the straight inductance strapH which extends vertically downwards from the plane of the paper to theother valve, and each jaw is connected to the associated grid terminalsfor example by the longitudinal member 25.

If the valves are required to operate on a wavelength slightly higherthan the minimum wavelength provided by the straight strap II at thelower ends of the anodes, the contact terminal members 12 maybeextended, as shown in Fig. 5, in the form of parallel bars 26longitudinally between which is arranged to slide a bar 21, the positionof which may be adjusted as will be fully understood, for varying theWavelength more or less above the minimum, when the bridging memberssuch as l5 are between the faces l0 and [2.

Referring lastly to Figs. 6 and 7 which represent a modification of thearrangement shown in Fig. 5, the terminals 28 of a pair of push-pullvalves, for instance grid terminals thereof, may have secured to themannular members 29 carrying longitudinal contact faces 39 between whichare arranged the straight bar inductance 3i and the inductance 32 havinga semi-circular or larger loop. These inductances have contact terminalmembers 33, 34 so that the bridge [5 may be moved along the contactfaces 30 to engage either the inductance terminal member 34 or theinductance terminal member 33 whereby to vary the inductance value to arelatively small extent.

Instead of all the engaging contact faces. such as H1, 12 being plane,certain of them may have straight or arcuate knife edges so as to:obtain a more efficient high frequency contact in the manner describedwith respect. to. Fig; 8' of said Application Serial No. 516,103 filedof even date; herewith, this particular feature being: a subsidiaryfeature of the present invention, but be:- ing more particularly claimedin the application lust above mentioned.

Reverting to Fig. 3 of the accompanying drawings the parallel lines 35indicate. feedersby which the oscillations from the two valves; may betaken away, for instance to a di-pole aerial (not shown). It. willbeunderstood; however, that inductive or capacity couplings: may beemployed alternatively to the conductive coupling illustrated in Fig. 3.

We claim:

1. A short wave radio transmitterhaving wave changing arrangements andincluding a valve having an electrode terminal member; said memberhaving a switch contact face, an inductance including a terminal memberhaving a contact face spaced from said first face only a. sufiicientdistance to withstand the working voltage between said faces, and a'movable contact having opposed faces adapted to be brought into; and:outof engagement with the-two first menti'oned contact faces.

2. A short wave radiotransmitter having wave changing arrangements: andof the character-de finedv in claim 1, wherein. one of. eacli pair ofopposeidi contact faces is provided. with aknifeedgei.

3.. A. radio. transmitter of the: character defined; in claim 1, whereinthe arrangements: are (1111311;- cated symmetrically for apai'r ofpushepullavalves. and; with the inductance between; them and; includingtwo contact: faces, one. opposite: the: con:- tact face of each valveelectrodea terminal;

4. A short wave radio: transmitter having: wane. changing arrangementsand. including a. valves having an electrode terminal member,v said member having an elongated switch: contact. face, a plurality ofinductanceseach including a contact face, each of said inductancecontact faces being opposite a different longitudinal portion of saidelongated contact face and being spaced from the latter only asufiicient distance to withstand the working voltage between said faces,and a movable contact having opposite faces adapted to be brought intoand out of engagement with opposed contact faces.

5. A short wave radio transmitter having wave changing arrangements andof the character defined in claim 4, wherein one of each pair of opposedcontact faces is provided with a knife edge.

6. A radio transmitter of the character defined in claim 4, wherein thearrangements are duplicated symmetrically for a pair of push-pull valvesand with the inductance between them and including two contact faces,one opposite the elongated contact face of each valve electrodeterminal.

7. A short wave radio transmitter having wave changing arrangements andincluding a valve having an electrode terminal member, said memberhaving a plurality of spaced contact faces, a plurality of inductanceseach including a contact face, each of said inductance contact facesbeing opposite one of said first-mentioned contact faces and beingspaced from the latter only a sufiicient distance to withstand theworking voltage between said faces, and a movable contact havingopposite faces adapted to be brought into and out of engagement withopposed con- 7 tact faces. 7 V V 8. A short wave radio transmitterhavingwave changing arrangements and of the character de- 9. A radiotransmitter of the character defined in claim 7, wherein thearrangementsare duplicated symmetrically for a vpairrof push-pull valvesand with theinductance between them and having two contact faces, oneopposite a contact face of each valve electrode terminal.

10. A short wave radio, transmitter having wave changing arrangementsand including. a pair of valves each having an electrode terminalmember, each of said members being provided with a switch contact face,which two faces are opposed, an inductance betweenisaid faces comprisinga pair of spaced conductors and abar slidable upon and between saidconductors, each of said conductors including a face to oppose a valveterminal member face, a movable contact including two bars, each of,said bars including opposed faces adapted to be brought into contactwith the face on one of said conductors and the opposed face of avalveelectrode terminal. 11. A short wave radio transmitter of the characterdefined in claim 10, wherein said movable contact is'pivoted and otherinductancesare positioned in its path of movement.

12. A short wave radio transmitter having Wave changing arrangements andincluding a valve having an elongated electrode terminal member, saidmember having a switchcontact face, an inductance including a terminalmember having a contact face spaced from said other face only asufilcient'distance to withstand the working voltage between said faces,a wave changing contact element pivoted upon said electrode terminal ata point remote from the position for minimum wave length, said contactelement having a length substantially corresponding to the length of thecontact face of said electrode terminal member, and a straight barinductance, including a 'contact'face positioned to be engaged by saidcontact element when .the latter is in the minimum wave length position.

13. A short wave radio transmitter having wave changing arrangements andincludingpa valve having an elongated electrode terminal member, saidmember having'a switchco'ntact face, an inductance including a terminalmember having a contact face spaced from said other face only asufficient distance to withstand the working voltage between said faces;a wave changing contact element pivoted upon said electrode terminal ata point remote from'theposition for minimum wavelength, said contactelement having a length substantially corresponding to the length of thecontact face of said electrode terminal member, a straight barinductance including a contact face positioned to be engaged by saidcontact element when the latter is in the minimum wave length position,

and a plurality of inductances each including a contact face adapted tobe selectively engaged by said contact element in other positions of thelatter to thereby change the wavelength. 7

JOHN MATHIESON DODDS. JOHN HEYWOOD LUDLQW.

REFERENCES CITED The following references are of record in the} file ofthis patent:

UNITED STATES PATENTS Guy Mar. 31, 1942

